Grease composition containing ethylene-vinyl acetate copolymer



United States Patent O 3,453,211 GREASE COMPOSITION CONTAINING ETHYL-ENE-VINYL ACETATE COPOLYMER Rodger W. Phillips, Glen Mills, Pa.,assignor to Sun Oil fompany, Philadelphia, Pa., a corporation of Newersey No Drawing. Filed Nov. 7, 1967, Ser. No. 681,117 Int. Cl. C10m5/10 U.S. U. 25237 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OFTHE INVENTION Greases that resist water wash off have been highlydesirable in the automotive accessory field, for example, as lubricantson door latching mechanisms. As a result many attempts have been made toimprove the adhesion and cohesion of greases.

Recently a successful water wash off resistant grease was shown in US.Patent No. 3,290,244 to Arthur T. Polishuk and Herbert L. Johnson. Thesuccessful greases employ weight percent oil soluble atacticpolypropylene or 0.3-5 weight percent oil-soluble atacticethylenepropylene copolymer. Both of these polymers are the byproductsof polymerizations directed to the production of the valuble and usefulisotactic polymers. Because of recent technological and economicaladvances the supply of low cost atactic materials is dwindling. It hasbecome necessary to develop new greases with water wash off resistantproperties and to that end the present invention is directed.

SUMMARY OF THE INVENTION DESCRIPTION OF THE INVENTION AND PREFERREDEMBODIMENTS The greases of the invention contain a major proportion of amineral lubricating oil. The proportions and percentages in relation tothe components of the grease in this specification are by weight of thetotal grease composition. The oil can be any oil prepared byconventional petroleum refining techniques such as solvent eX- traction,sulfuric acid treatment, clay treatment and the like, provided that theoil employed has a sufliciently high aromatic hydrocarbon content. Thearomatic content of the oil should be at least 40 percent by volume andmore 7 preferably should be in excess of 60 percent by volume. There isvery little improvement in the water wash off 3,453,211 Patented July 1,1969 properties of greases made from oils containing less than 40 volumepercent to which ethylene-vinyl acetate has been added. This isattributable to the lack of solubility of ethylene-vinyl acetate in oilshaving less than 40 volume percent aromatic, which results in aninhomogenous grease. Normally the lubricating oil used in the greasecomposition will have a viscosity in the range of 35-180 S. U.S. at 210F.

The grease compositions of the invention also contain a thickener. Theamount of thickener used is a minor proportion but should be sufiicientto thicken the lubricating oil used to grease consistency. Normally theamount of thickener used will be 5-40 percent. Any conventionalthickener can be employed such as the fatty acid metallic soaps,inorganic thickeners such as colloidal silica and bentonite clay, etc.Since greases containing a fatty acid metallic soap as thickener havesuperior properties for many applications, they are preferred. The metalcomponent of the soap can be any of the known soap-forming metals suchas sodium, potassium, lithium, barium, aluminum, strontium, calcium,magnesium, etc. although preferably the metal is sodium, lithium,calcium, aluminum, or barium. The fatty acid component of the soap canbe derived from any fatty acid containing 10-25 carbon atoms, can besaturated or unsaturated, and can contain hydroxy substituents. As theterm fatty acid is used herein it includes only those fatty acids having10- 25 carbon atoms. Examples of suitable fatty acid metallic soapscontaining metal and fatty acid components as described include sodiumstearate, lithium stearate, lithium oleate, calcium ricinoleate, calciumoleate, aluminum palmitate, etc.

Although the suitable soaps described above are characterized in thatall acid anions of the soap molecule are derived from fatty acids, theterm fatty acid metallic soap also includes, for the present purpose,the fatty acid complex metallic soaps well known in the art. Thesesoaps, which have also been referred to in the art as complex soaps,complex soap-salts, etc., contain a polyvalent soap forming metal as thecation of the soap molecule while the anions of the soap molecule arederived from both fatty acids and relatively low molecular weightorganic acids. The relatively low molecular weight organic acid anionpresent will depend mainly upon the polyvalent metal present. Where thepolyvalent metal is aluminum the anion is preferably the anion of anaromatic monocarboxylic acid containing 7-12 carbon atoms. Preferablythe anion is that of benzoic acid. Where the polyvalent metal is analkaline earth metal such as calcium, or barium the anion is preferablyderived from aliphatic monoand polycarboxylic acids containing 2-7carbon atoms. Preferably the anion is that of acetic acid. The fattyacids and polyvalent metals suitable for use in forming fatty acidcomplex metallic soaps are as previously described. Preferably thepolyvalent metal is calcium, aluminum, or barium. Examples of fatty acidcomplex metallic soaps having metal and acid components as describedabove are aluminum benzoate stearate, aluminum palmitate toluate,calcium stearate acetate, barium oleate propionate, barium linolenateacetate, etc.

The complex soaps can be prepared by methods well known in the art. Thusaluminum benzoate stearate is precipitated from an aqueous solution ofsodium stearate and sodium benzoate by the addition thereto of aluminumsulfate. The ratio of benzoate anions to stearate anions in theresulting soaps is determined by the ratio of sodium benzoate to sodiumstearate in the aqueous solution. For grease purposes the ratio ofbenzoate anions to stearate anions in the soap is usually in the rangeof 0.2:1 to 5:1.

0 It is also well known to prepare the complex soap in situ in the oilcomponent of the grease composition. Thus a mixture of acetic acid andstearic acid is admixed with oil after which hydrated lime is added tothe admixture and allowed to react with the mixed acids to form thecomplex soap.

Of the fatty acid metallic soaps suitable for the present purpose thefatty acid complex metallic soaps are preferred because they generallyresult in greases having substantially higher dropping points than canbe obtained in greases prepared from the non-complex soaps such assodium stearate, calcium stearate, aluminum stearate, etc.

The preparation of ethylene-vinyl acetate copolymer is known in the art.Preparations are shown in United States Patent No. 2,200,429 to Pe-rrinet al. and Canadian Patent No. 657,977 to Strauss dated Jan. 29, 1963.Generally, the preparation involves copolymerizing a mixture of ethyleneand vinyl acetate by means of a free-radicalproducing catalyst, such asoxygen or an organic peroxide at a pressure of 100 to 200 atmospheresand a temperature in the range of 150 C. to 250 C. and recovering theproduct. The proportion of vinyl acetate in the copolymer is unimportantfor the grease compositions of this invention. Generally suitablecopolymers will have 15 to 65 weight percent vinyl acetate, preferably17 to 42 weight percent.

From 0.5 to weight percent of the ethylene-vinyl acetate copolymer canbe added to the greases. Less than 0.5 weight percent of the copolymerprovides no improvement in the water wash off properties. Generally nomore than 2 weight percent of the copolymer will be employed in a usualgrease composition. For example, a grease containing 4 percent aluminumcomplex grease produced a rubbery product when 3 weight percent of thecopolymer was added. However, by lowering the soap content it ispossible to load more of the copolymer into the grease. This approachresults in gradual transition of the composition from a grease to asticky oil which lacks the stiifness and other requisite properties of agrease. It should be pointed out that a grease containing a reducedamount of soap and up to 10 weight percent ethylene-vinyl acetate oifersno greater wash off protection than an ordinary grease containing 2weight percent ethylenevinyl acetate.

The ethylene-vinyl acetate component of the grease can be incorporatedinto the grease during the preparation thereof or subsequently thereto.For example, most greases are prepared by adding the thickener to thelubricating oil at a temperature of about 200 F., stirring untiluniform, heating so about 350-500 F., and cooling to room temperature.Grease consistency is generally reached at some point in the coolingcycle. Where additives such as oxidation inhibitors are to be includedin the grease composition they are usually milled into the grease atabout 200 F. in the cooling cycle. The specific techniques employed varydepending mainly upon the actual thickeners used and are well known inthe art. The copolymer can be added to the oil at about the same timethe soap or other thickener is added to the oil, or, alternatively, canbe milled into the grease at some point, preferably about 300 F., in thecooling cycle. In either case the polymer dissolves in the oil toproduce a grease having improved adhesive-cohesive properties. In orderto improve the rate of dissolution of the polymer in the oil, it hasgenerally been found preferable to add the polymer to the oil at orabout the time the thickener is added, i.e., after addition of thethickener and prior to heating to the elevated temperature.

The following examples illustrate the invention more specifically. Thewater spray resistance test used to evaluate the greases in the examplesis the test (PETM #1015) presently used by General Motors Corp,Ternstedt Division, in order to determine the suitability of the greaseas an auto body hardware grease. Auto body hardware greases are used onautomobile door latches, door hinges, window mechanisms, etc. In such anapplication it is desirable that the grease not wash off when contactedby water. The test utilizes a chrome plated steel panels 2" by 6" by MTwo parallel lines on the panel divide it into three adjacentrectangular areas, the center area being 2" by 4", the two outer areasbeing 1'' by 2". The test panel is Weighed to the nearest 0.001 of agram. The 2" x 4" area is covered by a layer of the grease to be tested,thick, any grease outside of this area is removed from the panel. Thepanel is weighed to the nearest 0.001 of a gram and is then mounted 12"away from a nozzle attached to a water line. The nozzle used isidentified as Full Jet /z 66-25 and is manufactured by Spraying Systems,Inc., Chicago, Ill. Water at F. and at a nozzle pressure of 20 p.s.i.g.is sprayed onto the panel for a period of 5 minutes, after which thewater is shut off and the panel is dried at F. for 1 hour. Next anygrease on the two 1 by 2" outer areas is scraped off and the panel isagain weighed to the nearest 0.001 of a gram. The percent grease lost onpanel is calculated by:

X 100: percent grease lost on panel A=weight of clean dry test panelB=weight of initially greased test panel C=weight of spray exposedgreased test panel Example 1 2 weight percent of ethylene-vinyl acetatehaving a melt index of 45-65 and containing 39-42 weight percent vinylacetate sold under the trade name Elvax 40 by Du Pont Chemical Companywas added to a mineral oil containing about 46 percent aromatics havinga viscosity at 100 F. of about 500 SUS and API gravity at 60 F. of about20. This material was too fluid, i.e., merely a viscous oil. It was nota grease and could not be evaluated in conventional grease testingequipment.

Example 2 The same materials were employed as in Example 1 but 20 weightpercent of the copolymer was added to the oil. The composition still wasnot sufficiently stiif to test as a grease. An additional 20 weightpercent of the copolymer produced a solid rubbery, sticky material thatcould hardly be pulled apart and which could not be classified as agrease.

The grease compositions employed were prepared in the following manner:

The soap components were added to one half of the total volume of oil tobe employed at room temperature. The mixture was then heated to 240 F.and held at this temperature and stirred for about 20 minutes tocomplete the saponification. After the saponification the ethylene-vinylacetate copolymer, if any, is added. The balance of the oil is added andthe mixture is stirred until uniform. The mixture is then heated to atemperature of 400 F., held there for 5-10 minutes and is then cooled to200 F. where grease consistency has been reached. At this point anyfunctional additives, i.e., antioxidant etc. are blended in. The greaseis milled at 150 F. in a Gaulin Homogenizer at a pressure of 1000p.s.i.g. and is then allowed to cool to room temperature.

Example 3.-Lithium soap grease without copolymer Component: Wt. percentPetroleum oil 81.50 12 hydroxy stearic acid 4.25 12 hydroxy glycerides4.25 Lead naphthenate 2.00 Sulfurized sperm oil 8.00 Lithium hydroxide,lb./ lb. of fat 0.15

The petroleum oil is a blend of 53.00 parts by weight of an oilcontaining 45.5 volume percent aromatics and having a viscosity at 100F. of 300-320 SUS, API gravity at 60 F. of 19-22, and open cup flashpoint of 350 F. and 28.50 parts by weight of an oil containing 50.0volume percent aromatics and having a viscosity at 210 F.

of 130-140 SUS, API gravity at 60 F. of 17-14, and open cup flash pointof 490 F. The grease has a water wash off of 44.0 percent.

Example 4.Lithium soap grease with copolymer The same grease compositionas in Example 3 was prepared with 2 weight percent ethylene-vinylacetate copolymer, having melt index of 5-7 and containing 27-29 weightpercent vinyl acetate, based on the total weight of the grease. Waterwash oif was 7.7 percent.

Example 5 .Aluminum complex soap grease Without copolymer Component: Wt.percent Petroleum oil 84.35 Stearic acid 2.62 Benzoic acid 1.38 Kolate65 1 6.15 Penyl-Bmaphthyl amine 0.50 Zinc oxide 5.00 Diisopropoxypalmitate cyclic aluminum oxide trimercan be prepared according to 11.8.Patent 2,979,497 to Rinse. The petroleum oil is a blend of 56.00 partsby weight of an oil containing 46.0 volume percent aromatics and havinga viscosity at 100 F. of 500-530 SUS, API gravity at 60 F. of 18-21, andopen cup flash point of 370 F. and 28-35 parts by weight of an oilcontaining 50.0 volume percent aromatics and having a viscosity at 210F. of 130-140 SUS, API gravity at 60 F. of 17-19 and open cup flashpoint of 490 F. The water wash off was 12.0 percent.

Example 6.-Alu-minum complex grease with copolymer TABLE Soap typeLithium Aluminum complex Example 3 4 5 We ht percent ethylene-vinylacetate Water wash off, percent- Penetration, 60 strokes. Penetration,10,000 strokes Dropping point, F Shell roll stability, percent change inpen. (150 F., 100

hrs., r.p.m., 150 gr.) ASTM D-1263 (6 hrs., 220 F.,

90 gr.) wheelbearing, percent change in pen Sun wheelbearing, percentchange in pen. (6 hrs., 260 F.

130 gr.) (ASTM D-1263 modified as indicated) 1 Elvax 260-Du Pent.

It can readily be seen that compositions according to the presentinvention offer substantial and unexpected improvement in their adhesionand cohesion properties over the comparable grease compositions withoutthe ethylene-vinyl acetate copolymer.

The invention claimed is:

1. A grease composition comprising a major proportion of a minerallubricating oil containing at least 40 percent by volume of aromatichydrocarbons and a minor proportion of a thickening agent and an amountin the range of 0.5 to 10 weight percent of ethylene-viny1 acetatecopolymer.

2. A grease composition according to claim 1 wherein the ethylene-vinylacetate contains from 15 to weight percent vinyl acetate.

3. A grease composition according to claim 2 wherein the ethylene-vinylacetate contains from 17 to 42 weight percent vinyl acetate.

4. A grease composition according to claim 3 wherein the thickeningagent is a fatty acid metallic soap.

5. A grease composition according to claim 1 wherein the ethylene-vinylacetate copolymer is present in an amount in the range of 0.5 to 2weight percent.

6. A grease composition according to claim 3 wherein the ethylene-vinylacetate copolymer is present in an amount in the range of 0.5 to 2'weight percent.

7. A grease composition according to claim 4 wherein the fatty acidmetallic soap is a complex soap.

8. A grease composition according to claim 7 wherein the complex soap iscomplex aluminum soap.

9. A grease composition according to claim 8 wherein the ethylene-vinylacetate copolymer is present in an amount in the range of 0.5 to 2weight percent.

10. A grease composition according to claim 4 wherein the fatty acidmetallic soap is a lithium soap.

11. A grease composition according to claim 10whe1'ein theethylene-vinyl acetate copolymer is present in an amount in the range of0.5 to 2 weight percent.

References Cited UNITED STATES PATENTS 2,499,723 3/ 1950 Coifman et al25256 3,010,899 11/1961 Boyer 252-56 3,014,867 12/1961 Fronczak 252413,103,493 9/1963 Groszek et al 25241 3,173,965 3/1965 Pappas et a1 252593,250,714 5/1966 Ilnyckyj et a1. 25256 3,290,244 12/ 1966 Polishuk et al25259 DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner.

US. Cl. X.R. 25242, 5 6

